Lithographic Apparatus Matching via CD-Profile and Feature Analysis
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Solution Overview
Problem
Current methods for matching lithographic projection apparatuses are inaccurate due to the inability of critical dimension (CD) measurements to discriminate between various machine parameters, leading to errors in matching the optical transfer functions of different apparatuses.
Innovation Solution
A system comprising a monitored lithographic projection apparatus, a metrology apparatus, and a matching system that measures and compares CD-profile and further feature profile parameters to calculate corrected machine settings, ensuring accurate matching between lithographic projection apparatuses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CD measurements are used to match lithographic projection apparatuses, then the matching process can be performed, but the measurement precision is insufficient to discriminate between various machine parameters, leading to errors
Solution Approach 1:
The patent segments the single CD measurement into multiple independent measurements by introducing auxiliary structures (e.g., isolated lines, dense lines, different pitch structures) that respond differently to various machine parameters. This allows decomposition of the measurement into parameter-specific components, enabling discrimination between focus, exposure dose, and optical aberrations.
Solution Approach 2:
The patent introduces auxiliary measurement structures and intermediate calculation steps as mediators between the raw CD measurement and the final matching result. These intermediaries include measured quantities from different test structures, calculated focus metrics, and exposure dose estimates that bridge the gap between simple CD data and comprehensive machine parameter discrimination.
2Reliability
If multiple measurement parameters are introduced to improve discrimination capability, then the measurement precision and matching accuracy improve, but the device complexity and measurement process complexity increase
Solution Approach 1:
The patent designs auxiliary measurement structures that serve multiple functions simultaneously: they can measure focus, exposure dose, and optical aberrations depending on which structures are analyzed. The same set of test structures on the substrate serves as a universal measurement platform for multiple machine parameters, reducing the need for separate dedicated measurement systems.
Solution Approach 2:
The patent changes the parameters of the measurement structures (e.g., pitch, width, spacing, pattern geometry) to create structures with different sensitivities to various machine parameters. By varying these structural parameters, the system can selectively measure different parameters using the same basic measurement apparatus, avoiding the need for multiple complex specialized devices.
Data Source
AI summary
A lithographic system includes a monitored lithographic projection apparatus arranged to project a patterned beam onto a substrate. A scatterometer measures a plurality of parameters of the pattern transferred to the substrate including at least one CD-profile parameter and at least one further parameter of the pattern transferred to the substrate which is indicative of a machine setting of the monitored lithographic projection apparatus. A matching system includes a database storing information representative of reference CD values and reference values for the further feature. A comparison arrangement compares the measured values with the corresponding stored values, a lithographic parameter calculation means calculating a corrected set of machine settings for the monitored lithographic apparatus dependent on the differences between the measured and reference values.